Ventilation-perfusion mismatch: Difference between revisions
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== Overview == | == Overview == | ||
Ventilation Perfusion (V/Q) mismatch is said to have occurred when there is a there is defect in alveolar gas exchange in the lung either due to poor perfusion or reduced air entry. | Ventilation Perfusion (V/Q) mismatch is said to have occurred when there is a there is defect in alveolar gas exchange in the lung either due to poor perfusion or reduced air entry. It is a valuable tool in both understanding the normal physiology of lung and for diagnosing some of the common lung pathologies. | ||
In ideal physiologic conditions, V/Q ratio should be 1, that is 100 percent of the alveoli are recruited (full air entry), good oxygenation and 100 percent of the alveolar capillaries are perfused. However this does not happen even in healthy individuals as not all the alveoli in a healthy lung are recruited. The normal V/Q ratio is estimated to be 0.8. | Ventilation of air and perfusion of blood is not distributed equally in all the 400 million alveoli of our lung. This varies based on the effects of gravity, how patent the airways are and any pathological process that affect various parts of the lung. In ideal physiologic conditions, V/Q ratio should be 1, that is 100 percent of the alveoli are recruited (full air entry), good oxygenation and 100 percent of the alveolar capillaries are perfused. However this does not happen even in healthy individuals as not all the alveoli in a healthy lung are recruited. The normal V/Q ratio is estimated to be 0.8. An easy way to interpret this value of 0.8 would be that 80 percent of the alveoli in the lung have good air ventilation and blood perfusion. | ||
== | == Understanding V/Q mismatch in the context of hypoxia == | ||
There are five causes of hypoxia | |||
# Diffusion limitation | |||
# Hypoventilation | |||
# Low partial pressure of oxygen in inspired air | |||
# Shunt formation | |||
# Dead space formation | |||
The first three causes result in a normal V/Q and the last two result in an abnormal V/Q. | |||
==[[Ventilation-perfusion mismatch pathophysiology|Pathophysiology]]== | ==[[Ventilation-perfusion mismatch pathophysiology|Pathophysiology]]== | ||
Revision as of 08:52, 31 July 2018
Template:Ventilation-perfusion mismatch Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Ventilation Perfusion (V/Q) mismatch is said to have occurred when there is a there is defect in alveolar gas exchange in the lung either due to poor perfusion or reduced air entry. It is a valuable tool in both understanding the normal physiology of lung and for diagnosing some of the common lung pathologies.
Ventilation of air and perfusion of blood is not distributed equally in all the 400 million alveoli of our lung. This varies based on the effects of gravity, how patent the airways are and any pathological process that affect various parts of the lung. In ideal physiologic conditions, V/Q ratio should be 1, that is 100 percent of the alveoli are recruited (full air entry), good oxygenation and 100 percent of the alveolar capillaries are perfused. However this does not happen even in healthy individuals as not all the alveoli in a healthy lung are recruited. The normal V/Q ratio is estimated to be 0.8. An easy way to interpret this value of 0.8 would be that 80 percent of the alveoli in the lung have good air ventilation and blood perfusion.
Understanding V/Q mismatch in the context of hypoxia
There are five causes of hypoxia
- Diffusion limitation
- Hypoventilation
- Low partial pressure of oxygen in inspired air
- Shunt formation
- Dead space formation
The first three causes result in a normal V/Q and the last two result in an abnormal V/Q.